I play in a double knockout every year where you have a set period of time to play your match, say one week. You must contact your opponent and arrange where to play. After the match you call the organizer and tell him who won. Then the second round matches go and so on until the finals which are held at the organizers house with side games going on with all the players who were eliminated.
It's cool because you get a live game in once a week or so in your spare time.
Here is the double knockout bracket:
Bristol Street 2007 Heads-up Championship
Here is the format:
The Bristol Street Nightclub and Casino presents...
THE BRISTOL STREET 2007 HEADS-UP CHAMPIONSHIP 
$30 Buy-in - Double eliminiation $$$ Pay-out (assumes 32 players)$$$
1st place - 45% $432
2nd place - 25% $240
3rd place - 15% $144
4th place - 10% $96
5th place - 5% $48
Match Format
6,000 Chips - 20 minute blinds
25/25, 25/50, 50/100, 75/150, 100/200, 150/300, 200/400, 300/600
Player of the Year Points
1st - 57 points
2nd - 40 points
3rd - 33 points
4th - 28 points
5th - 25 points
6th - 23 points
7th(2 players) - 21 points
9th(4 players) - 18 points
13th(4 players) - 15 points
17th(8 players) - 0 points
25th(8 players) - 0 points
